Enzymatic pre-treatment of market pulp to improve fiber drainage and physical properties

ABSTRACT

Methods for reducing the effects of wetlapping, drying, and hornification of pulp fibers and consequently increasing the pulp drainage and strength properties in the final product (i.e., paper) are provided. The method which has been developed creates a “value-added” product by the wastepaper supplier or at the pulp and/or deinking (recycled paper) mill—a wastepaper load/bale, wet pulp stock or wet lap, or dried pulp treated with or impregnated with enzymes that enhance the quality of the pulp or paper product when it is repulped and processed at the paper mill.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of copending U.S. application Ser. No.13/323,136, filed Dec. 12, 2011, which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

The present invention is generally in the field of treating pulp,including wet lap or fully dried pulp, at virgin pulp and/or waste paperrecycling mills and/or treatment or impregnation of dry furnish loads orbales with enzymes prior to wetting in a wastepaper processing plant forthe purpose of combating the hornification/deterioration of pulp qualitythrough the wet-lapping, drying and recycling processes and producing agreater value virgin or recycled pulp for the eventual user of the pulpproduct.

BACKGROUND OF THE INVENTION

Current methods of producing virgin pulp utilize large manufacturingfacilities (pulp mills) that produce pulp for multiple end users. Pulpmills process pulp from softwood, hardwood logs or chips or non-woodsources into fibers which are used in the manufacture of paper. Methodsof processing virgin pulp to remove lignin to varying degrees range frompurely mechanical methods such as grinding logs and wood chips intoindividual fibers, to chemical treatments of the tree chips or non-woodfibrous materials. These methods result in pulp fibers with differentoptical, physical, and archival properties.

Virgin pulp produced in the pulp mill is commonly used in one of threeways: 1) within a short time frame following production, in a liquidstock form; 2) in wet lap form in which the liquid pulp is dewatered toapproximately 45-50% solids for later use; or 3) in a dry lap form,which is dried pulp having approximately 90-95% solids. Pulp used withina short time (i.e., (1) or dewatered (i.e., (2)) are collectively,“never dried”. The dry lap form and also wet lap form may be traded andtransported for use in making paper at a later time, which may be fromone to three days after pulping or after transport, sale, or storage fora period of three months or more. The majority of commercial marketbleached pulp is made into dry lap or once-dried pulp, while recycled,market deinked pulp (MDIP) mills commonly produce recycled pulp ineither wet lap form or fully dried form. After the fully dried or wetlapped pulp is shipped to a paper, tissue, or paper board mill, it isre-pulped with water and made into paper products. The quality of pulpor fibers deteriorates during the wet-lapping, drying or repulpingprocesses. One way in which the pulp deteriorates is known ashornification, which includes reduced drainage, lowered waterabsorbance, decreased strength, stiffer fibers and greater finescontent.

The time between pulp manufacture and re-pulping of the once-driedmarket virgin pulp varies greatly (e.g., from only a few days topotentially several years) while the typical time for wet lapped marketpulps is from a few days to six months due to higher chances of moldgrowth and spoilage due to the higher moisture content. Any grade ofpaper may be produced from the market virgin or recycled pulps. Examplesinclude fine printing and writing papers, cardboard, linerboard,corrugated paperboard, corrugated containers, boxes, tissue and towels.Each of these grades requires the pulp to have certain physical andchemical properties as well as operational properties of the stock suchas good drainage. An important physical property is paper strength. Thephysical properties of never-dried or never-thickened (i.e., never wetlapped), wet-lapped, and fully-dried pulps differ greatly depending ontype of fibers. Normally, the thickening or wet-lapping process anddrying process hornify and crush the fibers, and materially worsen thestrength properties. The never-dried or never-thickened pulp providesthe greatest strength and drainage properties followed by wet-lappedpulp with the fully-dried pulp having the lowest measures of tensile andburst strength for each pulp fiber type and worst pulp drainageproperties. The drying process further impairs sheet bulk.

Paper mills employ physical and chemical methods to provide thenecessary physical and operational properties required to optimize theproduction and economic parameters of paper manufacture. The point/timeof application of these drainage and strength treatments (i.e., shortlybefore application of the pulp into the paper machine) is importantbecause it preserves fiber physical properties and may employ strategiessuch as charge deployment for which timing is critical.

One example of a physical strength enhancement approach is mechanicalrefining. Mechanical refining is conducted by applying energy to drivemetal plates or other metallic shapes with extremely small inter-platetolerances such that fibers are fibrillated as they are pushed throughthe plates. Fibrillating the fibers is especially important in thepreparation of virgin fibers that are otherwise too “stick-like” andlack the necessary micro fibrils to form the key physical entanglements,greater inter-fiber surface area, and hydrogen bonding sites thatprovide the important strength aspects of sheets. Micro fibrils createdfrom refining can be damaged through time, especially in the pressingand drying process. Consequently, most printing and writing andtissue/towel manufacturers that need further strength development,perform the mechanical refining to virgin and recycled pulps, andperform the mechanical refining of the pulps immediately beforeintroduction into the paper machine. The major objective is to increasethe fibrillation amount on fibers for better strength and at the sametime to maintain a certain level of drainage, since refining hurts thedrainage. For example, fibrils “catch” water and make it move moreslowly through the sheet. Further, fibers are cut and shortenedfollowing mechanical refining.

Chemicals used to treat pulp in order to create the necessary physicaland operational properties include synthetic compounds, naturallyoccurring compounds, and enzyme treatment. Because of the mechanisms ofthese chemicals, they are applied to the pulp, at most, shortly beforethe pulp is introduced into the machine chest or head box. Manysynthetic strength aids involve charged materials, for example, anionicand cationic polyacrylamide treatments, which function to bridge fibersin order to hold them together to increase strength, drainage orretention. Time-sensitivity of application relative to the paper machinehead box position is central to efficacy of polymeric treatments becauseelectrical charge (present due to the charged materials) can be afleeting, temporary effect. Charge chemistries are also weak and requirea particular balance in application, so having too much time betweenchemical treatment and the actual formation of the sheet can bedetrimental to strength development, drainage or retention. In mostcases, the application of charge-based polymeric dry strength chemicalshas been within or between a small number of process steps before thepaper machine head box. These application points can include the inletto the fan pump (the pump that delivers stock to the headbox), themachine chest (chest feeding the machine), the blend chest (before themachine chest), the final stock chests which feed into the blend chest(e.g., short and long fiber chests mixing into the blend chest), therepulper (the first step in taking fully dried or wet lapped pulp to lowconsistency), spraying chemicals on the forming wire or between sheetplies or onto the formed sheet or in a size press, or even in themachine, for example, spraying between sheet plies.

An example of a natural material which serves as a strength aid isstarch. Starch and tree gums have a “glue-like” effect on the fibers. Aswith synthetic polymeric treatments, effective treatment with starch isdependent on the application site. Starch is typically applied to pulpshortly before the pulp is introduced into the paper machine either inthe machine chest or the blend chest. However, it can also be applied onthe machine after the pulp has undergone some process steps. Forexample, starch treatment can be employed by spraying starch on thesheet or between plies of multi-ply sheets for better bonding strength.In other applications, the starch strength treatment occurs after thesheet is fully formed and dried as the sheet passes through a vat tore-wet the sheet with a high concentration starch solution (e.g., in asize press).

The use of enzymatic treatments in the paper mill for the purposes ofstrength and drainage improvement has been investigated. Enzymes havebeen applied at or in the production line, shortly before introducingthe pulp into the paper machine at similar points in the process towhere mechanical and pre-machine chemical treatments can be applied.Examples are the machine chest, the blend chest, the post-fractionationchests, and even in the repulper at higher consistency. U.S. Pat. No.6,066,233 to Olsen, et al. discloses treating ink free recycled fiberswith an enzyme mixture (cellulose and pectinase) to achieve betterdrainage and produce a paper product with no loss in brightness. Thetreated recycled pulp was formed into paper product directly, i.e.,there was no dewatering or wet-lapping or drying step between theenzymatic treatment and paper making. U.S. Pat. No. 5,110,412 toFuentes, et al. discloses treating pulp with an enzyme such as acellulase, hemicellulase or mixtures thereof. The pulp is treated withenzyme at the paper mill and then quickly used on the paper machine.U.S. Pat. No. 6,808,595 to Burns, et al. discloses treating fibersimmediately before introducing the fibers into the paper machine with ahydrolytic enzyme to form aldehyde groups, and further treating with thehardwood fibers with a cross-linking agent and/or starch that formsbonds with the aldehyde groups for better strength and low lintingduring the tissue production. See also, U.S. Pat. No. 6,635,146 toLonsky, et al. which discloses treating paper making fibers with acellulolytic enzyme from 5,000 to about 200,000 ECU per kg of fibersprior to forming a paper sheet out of the treated pulp directly. U.S.Pat. No. 5,507,914 to Sarkar, et al. discloses treating pulp with acellulolytic enzyme, refining the treated pulp, and then treating with acationic polymeric coagulant and an anionic polymer at the vertical tankof the papermaking process. U.S. Pat. No. 6,939,437 to Hill, et al.discloses treating pulp in a paper mill with at least one cellulolyticenzyme and at least one cationic polymer before the paper machine.

The methods described above apply the enzymatic treatments at a pointprior to introducing the pulp onto the paper machine or at some processsteps in the paper mill shortly before the manufacturing of the paper.Thus, the pulp end user has to apply these treatments just before orduring the paper making process. With respect to the wet lap or fullydried pulp, strength treatments in or immediately prior to the papermachine may not adequately compensate for the hornification which hasoccurred during the wetlapping or drying process and the storage andtransportation time. Thus, there is still a need for a method oftreating pulp, or a method to treat wastepaper in the furnish collectionor bailing process which is ultimately shipped to the recycling mill, todecrease the effect of hornification and storage time on pulp physicalproperties during wetlapping, drying, storage and transportation of thepulp.

It is therefore an object of this invention to provide a method forreducing the effects of wetlapping, drying, and hornification ordeterioration of the pulp following the wet-lapping or drying process.

It is also an object of this invention to provide wet lapped and fullydried pulp with improved drainage and fiber strength.

SUMMARY OF THE INVENTION

Methods for reducing the effects of wetlapping, drying, andhornification of pulp fibers and consequently increasing the pulpdrainage and strength properties in the final product (i.e., paper) areprovided. The methods which have been developed creates a “value-added”product at the wastepaper dealer or processer or at the pulp and/ordeinking mill, those being a wastepaper load or bale or wet lap or driedpulp treated with or impregnated with enzymes that will enhance thequality of the pulp product when it is rewetted and processed at thepaper mill. The method of enhancing paper strength or pulp drainage in avirgin pulp mill or a recycled stock preparation plant includes thesteps of administering an effective amount of enzyme formulation toeither the wastepaper furnish at the wastepaper processing/balingfacility or the wet pulp stock prior to dewatering and/or drying ordirectly to the dewatered or dried pulp prior to or after the wetlapmachine or the pulp dryer, at the pulp plant, to treat the pulp prior tosubsequent repulping for the manufacturing of paper products. The enzymemay be administered to:

(1) wastepaper furnish at the furnish processing or baling site,(2) wet pulp stock prior to the wet lap machine or pulp dryer, or(3) wet lap pulp or dry lapped pulp after wet lapping or pulp dryingwhile still in the deink plant or pulp plant

In one embodiment, the method includes the steps of (1) treating virginor deinked pulp in the deinking or pulping plant with an effectiveamount of one or more enzymes and, (2) dewatering the virgin or deinkedpulp to obtain wet lap or fully dried pulp having reduced hornificationand damage of the pulp. In a second embodiment, the method includes (1)treatment of virgin or recycled pulp immediately or shortly after thewetlapping or fully-drying process with an effective amount of one ormore enzymes to produce a wet lap or fully dried pulp having reducedhornification and damage of the pulp for the eventual papermaker usingthat pulp. In this embodiment, the pulp is impregnated at the deinkplant or pulp mill with the enzymes which will modify the pulp later. Ina third embodiment, the method includes the steps of treating the drywastepaper furnish paper or bales at the wastepaper collecting orpackaging facility with an effective amount of one or more enzymes forlater use in a wastepaper processing plant.

Enzymes that can be applied to treat pulp at the pulp mill, before thepulp is dried and shipped to a paper mill, include cellulases,hemicellulases, xylanases, pectinases, pectin esterases and pectin andpectate lyases or combinations thereof. The enzyme treated pulp may befurther treated at the paper mill with different methods to improvedrainage and strength. Additional treatments to improve drainage andstrength include, but are not limited to, mechanical refining andapplication of starch, dry strength or wet strength polymers. The enzymetreatment is performed at a temperature from about 10° C. to about 90°C. at ambient atmospheric pressure. More preferably, the enzymetreatment is performed at a temperature range between 15° C. and 60° C.Higher temperatures are possible depending on which enzyme formulationsare used. Applications can be in pulp stocks with pH ranging from 3.5 to9.5. A pH range of 4.5 to 8.0 is preferable for most enzymes. The enzymetreatment is effective to increase the strength and/or drainage of thepulp compared to untreated pulps and consequently to improve thestrength of sheets made from the enzyme-treated pulp when compared tosheets made from untreated pulp. Increases in pulp drainage may bedemonstrated using the Schopper-Riegler or Canadian Standard Freenesstests and various laboratory drainage tests.

The enzyme treated or impregnated wet lapped or fully-dried pulp withimproved drainage and fiber strength sells as a value added-product,having increased strength and/or drainage of the pulp and improvedstrength of sheets made from enzyme-treated pulp compared to untreatedpulps and sheets made from untreated pulp.

Wastepaper loads or bales treated or impregnated with enzyme formulationeffective to enhance drainage, strength and other pulp and paperproperties in the paper making process are also provided. These areproduced using the method of enhancing paper strength or pulp drainageduring the waste paper loading or baling process by administering aneffective amount of enzyme formulation to wastepaper loads or bales thatare later used to produce recycled papers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of the processing of pulp preparation in a virginpulp mill or wastepaper recycling mill and a paper mill using the pulpstocks, showing points of enzyme treatment to collected wastepaperfurnish or in the deink plant or pulp mill prior to the eventualrepulping of wet lap or dried pulp at a paper mill.

DETAILED DESCRIPTION OF THE INVENTION I. Definitions

Unless defined otherwise, all technical and scientific terms used hereinhave the same meanings as commonly understood by one of skill in the artto which the disclosed invention belongs. Publications cited herein andthe materials for which they are cited are specifically incorporated byreference.

The term “deinking plant” refers to a plant or mill which processeswastepaper into a recycled pulp which can be used to manufacture papereither onsite or offsite. Deinking plants remove various contaminantssuch as inks, fillers, coatings, and stickies/adhesives from wastepaperand produce clean recycled pulp to be used either onsite or offsite atpaper machines.

The term “effective amount” refers to any amount which results in apredetermined or desired outcome. For example, an effective amount of anenzyme formulation intended to enhance strength means the amount ofenzyme formulation which is effective to increase fiber strengthproperties in the final sheet compared to pulps not treated with thesame enzyme formulation under the same conditions.

The term “enzymatic fiber modification” refers to any alteration ormodification of the pulp fibers as a result of interaction with anenzyme. The modification can either be a direct or indirect result ofthe enzyme treatment.

“Recycled pulp” or “recycled fibers” refers to the pulp or fiber stockcomponents of a paper or paperboard furnish that is derived fromrecovered paper and paperboard or wastepaper.

“Drying” of the pulp does not include processing of the pulp on thepaper machine. As used herein, drying of the pulp refers to drying pulpthat is eventually re-pulped before being processed on a paper machine.“Once dried” and “fully dried” are used interchangeably.

“Wet lap” pulp refers to virgin or deinked recycled pulp which is notmade directly into paper, but rather is dewatered and pressed down to aroughly 45-50% solid content product which is then stored or shipped inbale or crumb cube form for later use.

II. Enzyme Formulations

Enzyme formulations for treatment of pulp in the pulp mill or deinkplant include one or more enzymes effective to increase fiber strengthand/or modify drainage of the pulp. Examples of enzymes that can be usedto treat pulp as described herein include, but are not limited to,cellulases, endo glucanases, cellobiohydrolases, hemicellulases,mannanases, xylanases, pectinases, gamanases, pectin and pectate lyases,lipases and laccases.

The enzymes are typically used in combination, although this is notessential and pulp may only be treated with one type of enzyme or oneclass of enzyme such as cellulases. In one embodiment, the enzymes areadded in a concentration ranging from between 5 to 600 enzyme activityunits per 100 g OD fiber. Preferably, the concentration of the enzymesis between 20 to 200 enzyme units/100 g OD of fiber. The enzyme unitscan be determined as described below.

Measurement of Cellulase (Endo-β-1,4-Glucanase) Activity (CMCU)

Endo-β-1,4-glucanases (EC 3.2.1.4) attack β-(1,4) linkages in amorphouscellulose, carboxymethylcellulose (CMC), and phosphoric acid-swollencellulose, to produce shorter-chain cellooligosaccharides that in turnmay be hydrolyzed to cellobiose and glucose by exo-glucanase and betaglucosidase. This method relies on degradation of CMC chains, whichcauses a measurable reduction in the viscosity of the CMC gum solution.The chemicals used to determine cellulase activity include 0.30% ofsodium carboxymethyl cellulose (CMC) gum, AQUALON® CMC 7 (HerculesIncorporated, Wilmington, Del.) in pH 5.2 500 mM acetate buffer as thesubstrate and using CELLULAST® 1.5L cellulase (Novozymes A/B, Denmark)as a standard cellulase with an activity of 20000 CMC Units/ml. Adiluted enzyme sample or filtrate sample is mixed with 10.0 ml of gumsolution for 10 minutes at 40° C. water bath and the viscosity ismeasured using Fisher Brand Glass Ubbelohde Viscometer Tubes. Thereduction in viscosity is converted to CMC units based on the standardcellulase CELLULAST® 1.5L.

Measurement of Amylase Activity (AU)

Amylase (EC 3.2.1.1) catalyzes the degradation of starch (amylose). Aniodine-iodide indicator solution can be used to indicate starchconcentration which is detected spectrophotometrically at 500 nm. Theamylase activity is determined using potato starch as a substrate. Thismethod is based on the break-down of starch and the reaction is followedby an iodine titration. The initial blackish-blue color is formed whenstarch solution is mixed with an iodine solution, and the blue color isreduced gradually into reddish-brown which is measured using aspectrophotometer at 500 nm. One amylase unit (AU) is defined as theamount of amylase which, under the standard testing conditions, (37° C.,10 minutes and pH 5.6 of 100 ppm starch solution), generates 1 micromoleof glucose per minute.

Measurement of Lipase Activity (PCU)

The APC™ assay is based on an enzyme-coupled reaction. Triglycerides arefirst hydrolyzed by the lipases to glycerols and free fatty acids. Theglycerols produced from the reactions react with adenosine triphosphate,glycerol kinase, and glycerol-peroxidase. A dye is formed which can bemeasured spectrophotometrically at 540 nm. The increase in absorbance at540 nm is directly proportional to free glycerol concentration in thesample. A quantitative determination of enzyme activity is made bytesting a known standard of lipase at multiple dilution rates to obtaina standard curve. The lipase activity is calculated by comparing theabsorbance attained to a standard lipase of known activity. The lipaseactivity is determined using APC™ Method according to U.S. Pat. No.7,067,244.

Measurement of Pectinase Activity (PU)

Pectinases break down 1.0% pectin solution (Sigma P-9135) with pH 5.0acetate buffer at 50 mM and results in galacturonic acid (BioChemika48280). The concentration of pectin in the solution is determined bymeasuring the content of galacturonic acid. The treatment of pectinsolution with sulfuric acid will develop a color in the presence ofcarbazole (Sigma C-5132), which measured at 520 nm, is proportional tothe total pectin concentration. One unit of pectinase activity is theamount of pectinase needed to produce one mole of galacturonic acid atpH 5.0, temperature of 40° C. in 50 mM acetate buffer per minute.

Measurement of Xylanase Activity (XU)

The substrate employed is azurine-crosslinked wheat arabinoxylan.endo-1,4-β-D-xylanases hydrolyze the xylan backbone, releasing watersoluble dyed fragments. The amount of released dyed fragments can bedirectly related to enzyme activity. The Xylazyme AX tablets are orderedfrom Megazyme International Ireland Ltd., Bray Business Park, Bray, Co.Wicklow, Ireland. The absorbance of these dyed fragments can be detectedspectrophotometrically at 590 nm. A quantitative determination of enzymeactivity is made by testing a known standard of xylanase at multipledilution rates to obtain a standard curve. The standard curve correlatesthe enzyme activity of a known standard xylanase with absorbance.Novozymes Pulpzyme® HC has a standard activity unit of 40,000 XU/ml.

Measurement of Gamanase Activity (GU)

Gamanase breaks down galactomannans, such as bean gum, to reducingsugars which are measured with the DNS method. Locust bean gum at 0.1%(w/w) is used as the gamanase substrate. Enzyme is diluted with pH 6.850 mM phosphate buffer, added to the bean gum solution and incubated at40° C. water bath for 20 minutes. Shake the samples well every 5-10minutes and stop the reaction using 0.10 mL of 1M Na₂CO₃ solution, andthen transfer 0.5 mL from each of the sample test tubes to glass testtubes to react with DNS solution and measure the absorbance at 575 nm.One unit of gamanase activity (GU/ml) is defined as the amount of enzymegenerating 1 mole of reducing sugar released from 0.1% locust bean gumat pH 6.8 and 40° C. per minute.

Measurement of Laccase Activity (LAMU)

Laccase units (LAMU) are based on the rate of oxidation of syringdazine.1 LAMU is defined as the amount of enzyme which, under standardconditions, such as pH 7.5 and 30° C., oxidizes 1 mole syringaldazineper minute. The laccase activity in LCU may also be determine using2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) as thesubstrate at 25° C. and pH 4.5. One unit of enzyme activity is definedas the amount of enzyme oxidizing 1 mole of ABTS per minute attemperature of 25° C. and pH 4.5.

The formulations can be provided in the form of a solution or granulatedor powder enzymes that include compositions that adjust for pH and saltconcentrations. In general, enzyme formulations can also include theappropriate buffer for optimal enzyme activity. One of skill in the artcan optimize the conditions to maximize enzymatic activity usingconventional techniques known in the art.

Commercially available enzyme formulations can also be applied in themethod described herein. For example, Enzymatic Deinking Technologies(EDT), markets a line of products for fiber modification under the tradename of REFINASE®. REFINASE® products contain enzyme mixtures with atleast one of the enzymes being a cellulase, endo-glucanase,cellobiohydrolase, hemicellulase, mannanase, xylanase, pectinase, pectinesterase, pectin and pectate lyase, gamanase, esterase, laccase orlipase. The dosage of the REFINASE® based on oven dried fiber or pulpranges from 0.001% to 0.4%, with 0.025% to 0.15% based on OD fiber beingmore preferred.

In some embodiments the enzymes may be introduced in a dried,granulated, encapsulated, or pelletized form. Stabilizers such as metalions and cationic polymers may optionally be added to the formulations.The enzyme formulations may be treated to improve storage stability. Amethod for producing solid granulates with improved storage stability isdescribed for example U.S. Publication No. 2007/0111920 by Bauer, et al.

The formulations may additionally include one or more dispersants, whichcan be surfactants and/or polymers which may be used, for example, toenhance stability or activity of the enzymes.

III. Methods and Materials for Enzymatically Treating Pulp

Methods for reducing the effects of hornification and deterioration ofpulp are described. The methods include treating virgin or recycled pulpat a pulp making plant, prior to transport to a paper making plant, withan enzyme formulation containing enzyme in an amount effective toincrease pulp drainage characteristics of virgin pulp or recycled pulpand improve the strength of sheets made from the pulp. The various stepsin the process of furnish collection and pulp stock preparation prior tomaking paper for both recycled and virgin paper are shown in FIG. 1.

In one embodiment, the pulp is treated with the enzyme formulation priorto drying into dry pulp (approximately 90-95% dry) or processing intowet lap pulp (approximately 45-50% dry). Prior to the drying orprocessing into wet lap pulp step refers to any time before the wetlapdewatering step used for wetlap pulps or the dewatering and drying stepsinvolved in the production of dry pulps.

In a second embodiment, the enzyme formulation is applied to dry or wetpulp or impregnated into a bale of dried pulp or sheets of dried pulp.The dried pulp may be allowed to cool to a temperature at which theenzyme is not inactivated before administration or impregnation of thepulp. Enzyme is impregnated into the bales of pulp in a liquid or solidform at the pulp mill, prior to transport to the paper processing mill,either immediately after baling or after transport to a temporarystorage facility. In this embodiment, there may be a period of a day, afew days, a week, a month, a few months, or longer prior to processingof the pulp at a paper product plant.

In a third embodiment, the enzyme formulation is applied to collectedwastepaper furnish at the furnish processing or baling center prior toshipment to the paper recycling plant.

The pulp may optionally be treated with additives such as stabilizersand dispersants. These additives may be added alone or together with theenzymes at the same addition locations or separately at differentlocations.

The enzyme formulation is typically applied as a solution to the pulpstock but could also be added in dried or granulated enzyme form.Timing, concentration, temperature, pH and pulp consistency all play arole in pulp stock preparation. The stage of the process in which theenzyme treatment is applied can vary.

Treatment of Pulp with Enzyme Formulations

Several operating parameters in the pulp mill such as temperature or pHcan be varied to alter the enzyme activity in order to modify pulp fibercharacteristics such as drainage and physical properties.

Timing/Location of Enzyme Application

The point of the process in the pulp mill or deink plant at which theenzyme is applied is dependent on a variety of factors such as (1) theincubation time of the enzyme with the pulp; (2) the amount of timebetween the enzyme treatment and the drying or wet lapping step; (3) theamount of time between the drying or wet lapping of enzyme treated pulpand the time the pulp is used on a paper machine; and (4) the waterloops in the pulp mill or deink plant. The incubation time of the enzymewith the pulp stock can vary. The pulp stock is treated with enzymeformulation for at least 1 minute, preferably more than five minutes,but the actual time can be for many months, while the pulp is in storageor transport, and the level of enzyme activity varies under theconditions of storage. Those skilled in addition of enzymes to warm, wetpulp stock will understand that the amount of enzyme activity will besubstantially higher than when enzymes are provided in dry powder formto cooled, baled dry pulp in storage. The pulp is enzymatically treatedfor a period of time and in an amount and under conditions resulting infiber modification and then the pulp is partially (i.e., formed into“wet-lap” pulp) or fully dried, then usually formed into bales.Alternatively, the wetlapped or dried pulp can be treated with enzymeafter the wetlapping or drying process but while still in the pulp millor deink plant. The dried pulp can be stored for at least up to threeyears before repulped and made into paper.

The enzyme treatment can be performed in tanks in the pulp mill beforethe final dewatering or drying step. Other equipment stages in which themethods can be performed include, but are not limited to, dump chests,bleach towers, feed tanks, high density towers, silo water, white watertanks and other parts of the mill where a minimum of 1 minute of contacttime occurs or where process waters from the pre-drying or pre-wetlapping dewatering step return to a suitable part of the process forenzyme effect. Alternatively, the enzyme treatment in the deink plant orpulp mill can be applied after the wetlapping or drying step.

In preferred embodiments, the enzyme is administered to the wet pulpstock for at least 1 minute, preferably 5 minutes to 6 hours, and morepreferably 10 minutes to 2 hours.

Temperature

It is well known in the art that enzyme activity is temperature and pHdependent. The enzyme treatments described herein are typicallyeffective at temperatures of from 10° C. to 90° C. The more preferredtemperature range is from about 15° C. to 60° C.

However, the temperature range can vary depending on the nature of theenzyme used and the optimal activity range for each enzyme.

pH

The pH of the pulp stock can generally be from about 3.5 to about 9.5for most enzymes, more preferably from about 4.5 to 8.0. The pH of thestock can be adjusted using pH modifiers such as alum or aluminates,certain acids, carbon dioxide, and various alkalis such as sodiumhydroxide.

Enzyme Concentration

The enzyme dosage depends on the specific enzyme and the other treatmentconditions, in particular pulp consistency and temperature.

The enzymes may be used alone or in combination. The enzymesconcentration preferably ranges between 5 to 600 enzyme units/100 g ovendried (“OD”) fiber. Preferably, the concentration of the enzymes isbetween 20 to 200 enzyme units/100 g OD of fiber. The enzyme units canbe determined as described herein. The effective amount of enzyme isthat which results in increased fiber drainage of the pulp relative tonon-enzyme treated pulp and/or which enhances paper sheet strength ofthe paper made using the enzyme treated pulp. The method can result inincreases in both fiber drainage and paper sheet strength (for papermade from the pulp).

In preferred embodiments, the enzyme is administrated to the wet pulpstock with a consistency of 0.1% to 35%, preferably 0.5% to 15%, andmore preferably 1.0% to 10%.

Determination of Pulp Strength

The enzymatically modified fibers can result in increased strength inthe final paper product. Fiber strength can be determined using manydifferent measures which conform to the strength needs of the papergrade. Certain grades such as tissue focus on machine direction andcross direction tensile strength targets. Fine printing and writinggrades also require tensile strength standards but additionally focus onsurface printing ability. Packaging grades require a broad assortment ofstrength parameters including tensile, tear, Mullen burst, ring crush,STFI/SCT test, Concora, plybond, sizing test or box crush tests. Each ofthese tests is conducted according to industry standard testingequipment and methods. Increased paper strength is any increase in paperstrength over the standard or usual paper strengths achieved relative tountreated paper or paper treated with a method such as starch, chemicalprocessing or refining. Paper strength can be measured using TAPPI testmethods T494 (tensile strength), T403 (burst strength), T414 (tearstrength), and other standardized industry procedures.

Determination of Pulp Drainage

Pulp drainage is determined by the rate and degree to which water drainsfrom a pulp stock. Two of the most widely used tests are the CanadianStandard Freeness test and the European Schopper-Riegler test. One literof 0.3% or 0.2% consistency pulp stock, respectively, is drained over aconical object and the quantity of water which passes through anoverflow tube is monitored. A quick draining stock creates a largeoverflow and results in a high number of ml of filtrate passing over thecone as calculated by a Canadian Standard Freeness test. Alternatemethods of tracking drainage use vacuum systems whereby the time rateand maximum degree of water removal from a pulp suspension are tracked.Improved drainage on a paper machine is noted by changes in flat boxvacuums or couch roll vacuums or the position of dry lines on aFourdrinier forming table. Additionally, improvements in drainage may benoted in reductions in final sheet moisture with all other factors(e.g., machine speed, vacuums, sheet grammage, drying section pressure)remaining constant.

Increased pulp drainage is any increase in pulp drainage over thestandard pulp drainage achieved without enzyme treatment as describedherein and with other drainage affecting measures being accounted for.

The enzymatically treated dried or wet lapped pulp is re-pulped at apaper mill before manufacturing paper. The re-pulping can be performedusing any re-pulping methods known in the art.

IV. Pulp and Pulp Fibers

Wet lapped and dried pulp with improved drainage characteristics andimproved fiber strength is obtained by treatment with an effectiveamount of an enzyme(s) to increase the strength and/or drainage of thepulp and improve the strength of sheets made from enzyme-treated pulpcompared to untreated pulps and sheets made from untreated pulp.

The pulp and pulp fibers can be derived from any of a number of sources.Pulp can be made from wood, fiber crops or other non-wood sources suchas wheat straw or rice straw or grass. Wood pulp comes from softwood andhardwood trees. Softwood trees include spruce, pine, fir, larch andhemlock. Hardwoods include eucalyptus, aspen and birch. One source offiber that is widely used due to its lower cost and ready availabilityis the market eucalyptus pulp (e.g., South American, Australian, orIberian varieties). Application of enzymatic treatments to eucalyptuspulps is especially beneficial due to the lower strength aspects of thisshort fiber, this fiber's lower cost, and the relative significantimprovement from enzymatic treatment in terms of drainage and strength.

The pulp can be virgin pulp or recycled pulp. Virgin pulp is pulp thathas never been made into a final paper product. Recycled pulp refers topulp that was recycled from waste paper such as through a deinkingprocess.

The consistency of the pulp stock to be enzymatically treated can bebetween about 0.1% and 35%, more preferably between 0.5% and 10%.Alternatively, enzyme treatment can be applied to wetlap or fully driedpulps in the pulp mill. Consistency is defined as the oven dry weight ofthe fiber divided by the total weight of the fiber and water in thestock suspension.

Currently, pulp is made and dried (partially or completely) in a pulpmill or deinking plant. The dried pulp is then used in a paper mill forprocessing into paper. In most instances, the pulp mill does not adjointhe paper mill where the paper machine is located, thus the pulp fromthe pulp mill must be transported to the paper mill for furtherprocessing. However, as a result of the distance between the pulp milland the paper mill it is not feasible to transport a wet pulp stocksupply of pulp (“never-dried pulp”) for example, through a pipeline orin a large wet stock tank truck or rail car. Transport requires a morestable pulp product which can be stored economically for a long periodof time as well as one which is not prohibitively expensive totransport. Wet pulp stock is significantly heavier than wet lap or fullydried pulp, and therefore significantly more expensive to transport.Therefore the pulp is fully or partially dried prior to transportationto the paper mill. In a preferred embodiment, the pulp is pulp thatultimately is dried and then re-pulped before the paper making process.In one embodiment, the pulp is mixed with the enzymes, as a powder orencapsulated in some sort of carrier, which then solubilizes andactivates when the pulp is re-wetted prior to processing in the paperprocessing plant. Enzyme-treated virgin or recycled pulp can be dried toeither wetlap (approximately 45-50% consistency or dry) or fully dried(approximately 90-95% dry) form.

Enzymatic fiber modification can result from increasing fibrillation offibers resulting in more hydrogen bonds on the fiber and physicalentanglement. Enzymatic fiber modification can also swell the outerlayer of the fiber, reducing its density, and therefore making thefibers more “refining-able” resulting in more fibrils and delaminationof outside fiber walls when processed through a mechanical refiner.Increases in drainage can occur due to the way in which the smallermicro fibrils from the enzyme treatment are produced or by certainchanges to the colloidal phase of the pulp stock which enhances thewater flow through the fibers.

In one embodiment, the enzyme fiber modification resulting in increasedfiber drainage does not affect the paper sheet strength. In anotherembodiment the enzymatically treated pulp has both increased pulpdrainage and paper sheet strength (for paper made from the pulp). It ispossible that the enzyme modification does not affect fiber drainage butdoes improve paper sheet strength. Thus, the treatment affects drainageand strength individually and in combination.

The enzymatically treated dried or wet lapped pulp is re-pulped at apaper mill before manufacturing paper. The re-pulping can be performedusing any re-pulping methods known in the art.

V. Wastepaper Loads or Bales Treated or Impregnated with EnzymeFormulation

Wastepaper loads or bales treated or impregnated with enzyme formulationeffective to enhance drainage, strength and other pulp and paperproperties in the paper making process can also be made by administeringan effective amount of enzyme formulation to wastepaper loads or balesduring the wastepaper collection that are later used to produce recycledpapers. An enzyme formulation can be applied as solid or liquid to thesurface, or more preferably, impregnated using high pressure nozzles tointroduce the enzymes into the loads or bales.

The present invention will be further understood by reference to thefollowing non-limiting examples.

EXAMPLES Example 1: Impact of Enzymatic Treatment and Wet Lapping andDrying on Fully Bleached Kraft Hardwood Pulp

Materials and Methods

Experiments were conducted to determine the effect of enzyme, the effectof starch, and the wetlapping, drying and repulping on the treated pulp.The sheets were produced from the treated and control pulps with thesimilar conditions as follows: treatment temperature at 45° C., stock atabout pH 6.4 with continuing mixing at 3.5% consistency for 45 minutes.The wet stock from the pulp mill was treated with enzyme alone andstarch alone and the individually treated stocks are compared tonon-treated stock. The non-treated stock, enzyme treated stock andstarch treated stock were then split into two portions. The firstportion was used for analysis as non-dewatered and dried stock. In thiscase the treated stock was measured for drainage and then sheets weremade to measure sheet physical properties. The second portion was usedfor analysis of the post dewatering and drying impact of the treatment.The stock was dewatered with filter paper to about 25%, pressed at 50psi for 2 minutes, and then dried on a speed dryer with surfacetemperature of 90-95° C. for 45 minutes. The dried pulp was thenrepulped with a disintegrator for 20k revolutions with tap water fordrainage and then made into a sheet to determine the effect ofwetlapping, drying and repulping following either enzyme or starchtreatment or a no-treatment control. Hand sheets were made, conditionedand measured according to TAPPI T402, T205, T220, T403, T220 and T411.

Results

Table 1 shows the effect on drainage and sheet strength of an enzymeblend, Refinase® A alone, starch alone, and no treatment, followed bywet lapping and drying process.

TABLE 1 Effect of enzymes and starch on drainage and strength propertiesof fully bleached Kraft hardwood pulp. Physical Refinase ®, Starch,properties Treatment conditions Control 0.05% 2.0% Freeness, mlNever-dried 635 673 598 Wet-lapped, 607 647 610 dried and repulpedBurst, kPa · m²/g Never-dried 2.0 2.8 2.4 Wet-lapped, 1.2 1.6 1.0 driedand repulped Tensile, N · m/g Never-dried 37.8 46.8 39.8 Wet-lapped,24.2 28.5 19.7 dried and repulped

The term “Never-dried” above refers to no interim dewatering orwetlapping/drying step of the wet virgin Kraft eucalyptus pulp stockdirectly from the pulp mill prior to sheet manufacturing. The“Dewatered, dried and re-pulped” above refers to the processing of thepulp which was wet-lapped using filtration, dried and repulped followingenzyme or starch treatment of the “Never-dried” wet pulp stock.

Treatment of never-dried pulp with starch improved the strengthproperties of pulp when compared to untreated pulp. The positive effectof the starch on strength did not carry through the wet-lapping anddrying process. By contrast, enzyme treatment improved strengthproperties of treated pulp, even for pulp after the wet-lapping anddrying process. As shown in Table 1, the enzymatic treatment isbeneficial for improved drainage and fiber properties for many types ofpaper production.

Example 2: Impact of Enzymatic and Starch Treatment on Deinked PulpStock

Materials and Methods

A similar set of experiments as described in Example 1 was conducted ondeinked pulp stock taken from the end of the deink plant where mixedoffice waste paper was a major furnish component. The deinked pulp wasvery clean with very low residual dirt. Its brightness was about 75%ISO. The deinked pulp was treated similarly as the virgin hardwood pulpused in Example 1.

Results

The results are shown in Table 2.

TABLE 2 Effect of enzymes and starch on drainage and strength of deinkedpulp stock Physical Refinase ®, Starch, properties Treatment conditionsControl 0.05% 1.0% Freeness, ml Never-dried 466 531 415 Dewatered, 438524 485 dried and repulped Burst, kPa · m²/g Never-dried 2.8 3.2 3.1Dewatered, 2.3 2.7 2.2 dried and repulped Tensile, N · m/g Never-dried43.7 51.6 47.6 Dewatered, 33.3 38.3 32.9 dried and repulped

The dewatering, drying and repulping once again showed significantdeterioration in pulp properties in terms of drainage and physicalstrength. The enzymatic treatment showed improvements in stock drainageand sheet strength compared to control results for both the never-driedand post-dewatering/drying treatments. By contrast, starch treatmentalone was not effective in improving pulp drainage or strengthproperties of the resulting sheets produced after dewatering and drying.

Example 3: Impact of Enzymatic Treatment of Fully Bleached KraftLoblolly Pulp

Materials and Methods

A wet pulp stock at about 3.6% consistency was collected from a southernKraft pulp mill which makes bleached dry lap commercial products. Thewet pulp stock was treated in a similar manner as described in Example 1for hardwood pulp using Refinase® B at 0.05% based on OD fiber.

Results

The results are shown in Table 3.

TABLE 3 Effect of enzyme on bleached Loblolly Kraft pulp PhysicalRefinase ®, Starch, properties Treatment conditions Control 0.05% 1.0%Freeness, ml Never-dried 682 729 589 Dewatered, 665 728 683 dried andrepulped Burst, kPa · m²/g Never-dried 2.7 3.1 3.0 Dewatered, 1.9 2.42.1 dried and repulped Tensile, N · m/g Never-dried 32.2 37.7 36.1Dewatered, 24.2 28.4 22.1 dried and repulped

As in examples 1 and 2, the enzymatic treatment of never-dried pulpsprovided material gains to drainage and strength which carried throughthe dewatering and drying process as compared to the non-treatedcontrol. As in the other examples, the starch treatment prior todewatering and drying failed to provide improvements in drainage of thepost dewatered and dried pulp and the strength tests were inferior tothose from the enzymatic treatment.

The methods described herein can be employed at a pulp mill to producewet lapped or dried pulp for later use. This would be beneficial in viewof the geographically dispersed users of the virgin and market deinkedpulps.

Those skilled in the art will recognize, or be able to ascertain impactusing no more than routine experimentation and equivalents to thespecific embodiments of the invention described herein. Such equivalentsare intended to be encompassed by the following claims.

1. Enzyme treated pulp selected from the group consisting of dried pulp,wetlap pulp, or pulp in the form of market pulp sheets, bales of marketpulp sheets, and dried crumbled pulp, wherein the treated pulp, whencompared to pulp not treated with enzyme, (1) has increased pulpdrainage characteristics when repulped, (2) produces sheets havingimproved strength when sheets are made from the repulped treated pulp,or (3) both, wherein the treated pulp was enzyme treated byadministering an effective amount of enzyme formulation to pulp (1)after dewatering and drying of the pulp into dried pulp, wetlap pulp, orpulp in the form of market pulp sheets, bales of market pulp sheets, ordried crumbled pulp and (2) prior to subsequent repulping for themanufacturing of paper products, wherein the administered enzymeformulation is effective (1) to increase pulp drainage characteristicsof the treated pulp when repulped, (2) to improve strength when sheetsare made from the treated pulp, or (3) both, and wherein the enzymeformulation has at least one enzyme activity selected from the groupconsisting of cellulase activity, pectinase activity, endo-glucanaseactivity, cellbiohydrolase activity, hemicellulase activity, mannanaseactivity, xylanase activity, gamanase activity, pectin lyase activity,pectate lyase activity, lipase activity, and laccase activity.
 2. Thetreated pulp of claim 1, wherein the pulp is recycled paper pulp.
 3. Thetreated pulp of claim 1, wherein the pulp is virgin pulp.
 4. The treatedpulp of claim 1, wherein the enzyme formulation is administered at avirgin pulp mill or a wastepaper recycling plant.
 5. The treated pulp ofclaim 4, wherein the enzyme formulation is administered at the virgin orrecycling pulp plant to wet lap pulp.
 6. The treated pulp of claim 4,wherein the enzyme formulation is administered at the virgin orrecycling pulp plant to dry lapped pulp.
 7. (canceled)
 8. The treatedpulp of claim 1, wherein the enzyme formulation is administered beforethe repulping of wetlap pulp as part of the paper manufacturing process.9. (canceled)
 10. The treated pulp of claim 1, wherein the enzymeformulation comprises one or more enzymes selected from the groupconsisting of cellulases, endo-glucanases, cellobiohydrolases,hemicellulases, mannanases, xylanases, pectinases, gamanases, pectinlyases, pectate lyases, lipases and laccases.
 11. The treated pulp ofclaim 10, wherein the enzyme formulation is administered as a liquid orsolid.
 12. The treated pulp of claim 11, wherein the enzyme formulationis administered as a powder, dried, granulated, encapsulated, orpelletized form.
 13. The treated pulp of claim 1, wherein the enzymeformulation is dosed with enzyme activity ranging from 5 to 600 units ofenzymatic activity per 100 gram oven dried fiber. 14-17. (canceled) 18.The treated pulp of claim 1, wherein the properties of the paperproducts made from the pulp are altered as compared to paper productsmade from the pulp not treated with the enzyme formulation. 19-21.(canceled)
 22. The treated pulp of claim 1, wherein the pulp is driedpulp.
 23. The treated pulp of claim 1, wherein the pulp is wetlap pulp.24. The treated pulp of claim 1, wherein the pulp is in the form ofmarket pulp sheets, bales of market pulp sheets, or dried crumbled pulp.25. The treated pulp of claim 1, wherein the enzyme is impregnated intomarket pulp sheets, bales of market pulp sheets, or dried crumbled pulp.26-27. (canceled)
 28. The treated pulp of claim 1, wherein the treatedpulp is not processed at a paper making plant for a week or longer afteradministration of the enzyme formulation.
 29. The treated pulp of claim1, wherein the enzyme formulation has cellulase activity, pectinaseactivity, and at least one enzyme activity selected from the groupconsisting of endo-glucanase activity, cellbiohydrolase activity,hemicellulase activity, mannanase activity, xylanase activity, gamanaseactivity, pectin lyase activity, pectate lyase activity, lipaseactivity, and laccase activity.
 30. The treated pulp of claim 29,wherein the enzyme formulation comprises one or more enzymes, whereinthe one or more enzymes comprise at least one cellulase, at least onepectinase, and at least one enzyme selected from the group consisting ofendo-glucanases, cellobiohydrolases, hemicellulases, mannanases,xylanases, gamanases, pectin lyases, pectate lyases, lipases andlaccases.
 31. The treated pulp of claim 1, wherein the enzymecomposition is administered at a virgin pulp mill.
 32. The treated pulpof claim 1, wherein the administration of the enzyme formulationimpregnates the dried pulp, wetlap pulp, or pulp in the form of marketpulp sheets, bales of market pulp sheets, or dried crumbled pulp withthe enzyme formulation.
 33. Enzyme treated dried pulp, wetlap pulp, orpulp in the form of market pulp sheets, bales of market pulp sheets, ordried crumbled pulp, wherein the treated pulp, when compared to pulp nottreated with enzyme, (1) has increased pulp drainage characteristicswhen repulped, (2) produces sheets having improved strength when sheetsare made from the repulped treated pulp, or (3) both, wherein the pulpwas enzyme treated by administering, in a virgin pulp mill, an effectiveamount of enzyme formulation to virgin pulp after bleaching of the pulpand prior to dewatering and drying of the pulp into the dried pulp,wetlap pulp, or pulp in the form of market pulp sheets, bales of marketpulp sheets, or dried crumbled pulp, wherein the administered enzymeformulation is effective (1) to increase pulp drainage characteristicsof the treated pulp when repulped, (2) to improve strength when sheetsare made from the treated pulp, or (3) both, and wherein the enzymeformulation has cellulase activity, pectinase activity, and at least oneenzyme activity selected from the group consisting of endo-glucanaseactivity, cellbiohydrolase activity, hemicellulase activity, mannanaseactivity, xylanase activity, gamanase activity, pectin lyase activity,pectate lyase activity, lipase activity, and laccase activity.
 34. Thetreated pulp of claim 33, wherein the enzyme formulation is administeredprior to the pulp dryer.
 35. The treated pulp of claim 33, wherein theenzyme formulation is administered prior to the wet lap machine.
 36. Thetreated pulp of claim 33, wherein the enzyme formulation comprises oneor more enzymes, wherein the one or more enzymes comprise at least onecellulase, at least one pectinase, and at least one enzyme selected fromthe group consisting of endo-glucanases, cellobiohydrolases,hemicellulases, mannanases, xylanases, gamanases, pectin lyases, pectatelyases, lipases and laccases.
 37. The treated pulp of claim 36, whereinthe enzyme formulation is administered as a liquid or solid.
 38. Thetreated pulp of claim 37, wherein the enzyme formulation is administeredas a powder, dried, granulated, encapsulated, or pelletized form. 39.The treated pulp of claim 33, wherein the enzyme formulation is dosedwith enzyme activity ranging from 5 to 600 units of enzymatic activityper 100 gram oven dried fiber.
 40. The treated pulp of claim 33, whereinthe enzyme is administered at a temperature in the range of 10° C. to90° C.
 41. The treated pulp of claim 33, wherein the enzyme isadministered at a pH range of 3.5 to 9.5.
 42. The treated pulp of claim33, wherein the enzyme is administered for at least 1 minute.
 43. Thetreated pulp of claim 33, wherein the enzyme is administered with aconsistency of 0.1% to 35%.
 44. The treated pulp of claim 33, whereinthe properties of the paper products made from the pulp are altered ascompared to paper products made from pulp not treated with the enzymeformulation.
 45. The treated pulp of claim 33, wherein the pulp is driedpulp.
 46. The treated pulp of claim 33, wherein the pulp is wetlap pulp.47. The treated pulp of claim 33, wherein the pulp is in the form ofmarket pulp sheets, bales of market pulp sheets, or dried crumbled pulp.48. The treated pulp of claim 33, wherein the treated pulp is notprocessed at a paper making plant for a week or longer afteradministration of the enzyme formulation.